The present invention relates to a method for prevention of reduction with elapse of time in nitrile hydration activity of nitrilase produced by a specific microorganism and for stable preservation of this activity.
In recent years, the technology of immobilized enzymes and microorganisms has developed rapidly, resulting in increasing attempts to utilize microorganisms and enzymes as they are or in the immobilized state as catalysts for various single or complex chemical reactions.
Nitrilase has been known as an enzyme capable of hydrating nitriles to produce the corresponding amides. As examples of the utilization of this enzyme, methods for producing (meth)acrylamide from (meth)acrylonitrile with the use of microorganisms of the genus Corynebacterium or Nocardia which produce nitrilase (Reference: Japanese Patent Pub. No. 17918/1981); for producing from C.sub.2-4 nitriles the corresponding amides with the use of microorganisms of the genus Rhodococcus (Reference: Japanese Patent Appln. No. 452/1985); and for producing from nitriles the corresponding amides with the use of microorganisms of the genus Bacillus, Bacteridium, Micrococuss or Brevibacterium (Reference: Japanese Patent Laid-Open Pub. No. 86186/1976) have been proposed.
As a result of further investigation, however, we have found that the nitrile hydration activity of the above mentioned nitrilase is labile and decreases as the temperature rises or the purity of the enzyme increases. This decrease occurs also with immobilized enzymes.